Relationship between particle size and radiocesium in fluvial suspended sediment related to the Fukushima Daiichi Nuclear Power Plant accident

We collected fluvial suspended sediments in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident and analyzed the ¹³⁷Cs concentration in bulk and size-fractioned samples to investigate the particle-size-dependent distribution of radiocesium. The ¹³⁷Cs concentration in bulk suspended sediments decreased from August to December 2011, possibly reflecting a decrease of radiocesium concentration in its source materials. Smaller particles had higher radiocesium concentrations, reflecting larger specific surface areas. Silt- and sand-size fractions occupied more than 95 % of the total ¹³⁷Cs in the suspended sediments. The contribution of clay-size fractions, which had the highest ¹³⁷Cs concentration, was quite small because of their low frequency. A line of the data showed that the particle size distribution of radiocesium was essential to evaluate the migration and distribution of radiocesium in river systems where radiocesium is mainly present as particulate form after the FDNPP accident.     

Local distribution of radioactivity in tree leaves contaminated by fallout of the radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant

We analyzed fresh and dead leaves collected in forests in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, using autoradiography. Both fresh and dead leaves of Cryptomeria japonica were contaminated by radionuclides (¹³⁴Cs and ¹³⁷Cs). Contamination of the fresh leaves was possibly attributed to interception of radionuclides by tree canopies, whereas the dead leaves indicated the direct deposition of radionuclides by fallout and/or washout of radionuclides intercepted by tree canopies. Translocation of radiocesium from a contaminated branch to new leaves growing after the FDNPP accident was not clearly observed, although transfer of radiocesium from leaf parts to male flowers occurred. Fallen leaves of Quercus serrata, which started growing after the FDNPP accident, did not show radioactivity, indicating that significant amounts of translocation from other parts to new leaves did not occur. Fallen leaves of Q. serrata collected from a litter showed hot spots originating from direct fallout. Needles of Pinus densiflora were also contaminated by fallout. Leaching with pure water removed soluble fractions of radiocesium and hot particles from the surface of the contaminated leaves, but significant amounts of radioactivity remained. This means that foliar absorption occurred in both fresh and dead leaves. Further leaching experiments using surfactant and acetone could not remove the remaining radiocesium from the leaves. The leaching experiments indicate that radiocesium in the contaminated leaves is strongly fixed in leaf tissues and is not readily released unless leaf tissues are decomposed.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake and release of radiocesium by bottom sediment and suspended solids from a small stream were studied as a function of contact time during the uptake and releases, of concentration of the solid phases and of temperature, using laboratory model experiments. Kinetics of the uptake were found to be singificantly affected by temperature and concentration of the solid phase. The kinetics and the concentration effect can be quantitatively described using kinetic model of two parallel or consecutive reactions. Kinetic parameters for the model were determined. Distribution coefficient K_d is independent of sediment concentration in the range of 20–70 mg·dm^?3 but passes through a maximum at higher concentration values. Release of radiocesium adsorbed on the freshwater solids was found to be quite rapid and a simple kinetics of the release from freshwater solids was observed. The amount released decreased with increasing contact time of radiocesium with solid phase. Quantitative evaluation of the release revealed partial irreversibility of radiocesium uptake on the solids studied. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modeling of radiocesium migration in rivers.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake of radiocesium by bottom sediments and suspended solids from small streams was studied as a function of pH and composition of aqueous phase, of the concentration of cesium in water and of the composition of freshwater solids, using laboratory model experiments. pH had negligible effect on the uptake in the pH range 5–9, the uptake decreased at pH values less than 3–5 depending on the nature and concentration of the solids. Addition of cations suppressed the uptake in the order K⁺>Na⁺>Ca²⁺, the suppression began at 0.001, 0.01 and 0.1 mol.dm^?3 concentration, respectively. Increase in cesium concentration in water caused a decrease of radiocesium uptake, but at very low concentrations of cesium combined with higher concentration of sediment (2g·dm^?3) the uptake was independent of cesium concentration. Removal of carbonates, oxidic coatings and organic matter from a sediment did not affect the sorption properties of the sediment. The nature of the effects found confirms that cesium is sorbed mainly by clay components of freshwater solids. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modelling of radiocesium migration in rivers.     

Mobility of 137Cs Related to Speciation Studies in Contaminated Soils of the Chernobyl Area

Chernobyl derived ¹³⁷Cs present in upper soil layers can still remain available to cation exchange and hence to downward migration. More than its physico-chemical deposit forms (fuel particles and/or condensed aerosols), radiocesium mobility is influenced by soil properties. Although all the soils studied contain illitic clay minerals, different ¹³⁷Cs fixation levels were observed due to: (1) the reactivity state of sorption sites with a low radiocesium content in soil, and (2) the presence, or absence, of organic matter complexes inhibiting cation sorption on clays.     

Sorption of radiocesium on soils in the presence of electrolytes

The influence of background electrolytes (KCl, NH₄Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg^–1.     

Effect of <Emphasis Type="Italic">Deinococcus radiodurans</Emphasis> on speciation of radiocesium in soil

The chemical speciation of radiocesium which determines its environmental behavior could be affected by microbial processes in soil. However, the speciation of radiocesium in soil has not been well documented. The speciation of radiocesium in soil was investigated with the absence and presence of Deinococcus radiodurans and Pseudomonas sp., respectively. The content of radiocesium in residual phase was increased significantly (p<0.01) with the presence of bacteria in comparison to aseptic control, about 60% of adsorbed radiocesium existed in residual phase with the presence of bacteria. The proportions of radiocesium in different speciation were not significantly changed in the presence of D. radiodurans and Pseudomonas sp. with a longer incubation time. About 67.8% of the total absorbed radiocesium in D. radiodurans cells was extractable with ethanol.     

EB-radiolysis of carbamazepine: in pure-water with different ions and in surface water

A method for the rapid and simultaneous monitoring of particulate and dissolved ¹³⁷Cs concentration in water was developed. This method uses pleated polypropylene nonwoven fabric filter to collect particulate radiocesium, and nonwoven fabric impregnated with Prussian blue (PB) to absorb dissolved radiocesium. The fabric was placed into cylindrical plastic cartridges (SS-cartridge and PB-cartridge). Traditional monitoring methods, such as evaporative concentration, often require time for pre-processing. However, this method described requires much less pre-processing time before the detection. Experiments conducted with simulated river water demonstrated that almost all of the suspended solids weight was collected in the SS-cartridge, and that more than 92 % of dissolved ¹³⁷Cs was absorbed onto the two PB-cartridges by 2.5 L/min flow rate when the range of the pH was 6–8. This device was applied to monitor Abukuma River water at two locations and the results were compared with those obtained using the filtrating and evaporative concentration method. The suspended solids concentration in river water, calculated by weight gain of the SS-cartridge and by sediment weight after filtration with a 0.45-μm membrane filter, agreed well. The radioactivity of the particulate and dissolved ¹³⁷Cs also agreed well in one of the two replications of this method. In addition, the required time for pre-processing was reduced by 60 times that by filtrating and evaporative concentration method. This method can separately collect and concentrate particulate and dissolved radiocesium rapidly and simultaneously in the field.     

Uptake of radiocesium and alkali metals by mushrooms

Various mushrooms and soils were analyzed for alkali metals and for radiocesium. The obtained concentration factors of the nonradioactive Cs for mushrooms are not significantly different from that for vascular plants, whereas in the case of radiocesium the values found were orders of magnitude higher. The different behaviour of natural and radioactive cesium may be due to their disequilibrium in the ecosystems. The irradiation of man due to ingestion of contaminated mushrooms cannot cause a significant health risk.     

Effect of pH, temperature, conductivity and sediment size on thorium and radium activities along Jucar River (Spain)

A study is presented on the distribution of thorium and radium isotopes in sediments, suspended matter and water collected along Jucar river (East of Spain), using low-level α-spectrometry. The first aim of this work is to study the thorium and radium activity in water, sediment and suspended matter and their dependence on pH, temperature, conductivity and sediment sizes along Jucar river. The analysis of activity variation with these parameters will provide information about the dynamics of these radionuclides in rivers. The values obtained for the distribution factors between suspended matter and water (K _d ) are also discussed.     

Sorption and desorption of radiocesium on calcareous soil: Results from batch and column investigations

The sorption and desorption of radiocesium on a calcareous soil from Jiuqian County of Gansu Province (China) were studied by using batch and column experiments. The sorption-desorption isotherms and the breakthrough curves, displacement curves on the whole soil and two treated soils were determined. Based on these results, it was found that the sorption and retention of cesium are mainly determined by the clay minerals, that the sorption-desorption hysteresis of cesium on the calcareous soil is obvious and that the organic matter has a little positive contribution and the calcium carbonate has a little negative contribution to the sorption of cesium on the whole soil. The results from batch experiments were consistent with the results from column experiments.     

Radiocesium sorption-desorption processes in lake sediments

The kinetics of radiocesium sorption and desorption by cation solutions and the corresponding radiocesium distribution profiles in sediment cores were investigated. The results have shown that a significant percentage of radiocesium is adsorbed in the sediments during the first 3 d. Radiocesium reaches rapidly (< than 5 d) at a depth which does not exceed 3.5 cm. The desorption of radiocesium was found to depend on cation concentrations. Empirical laws are derived both for cesium adsorption and desorption.     

Fukushima-derived radiocesium in the western North Pacific in 2014

Journal of Radioanalytical and Nuclear Chemistry - In 2014, we measured activity concentration of radiocesium in the western North Pacific Ocean. In the north of Kuroshio Front high activity...     

Assessing the deposition and remobilisation behaviour of metals between river water and river sediment using partial least squares regression

Partial least squares regression (PLS) as a method for multivariate data analysis has been applied to environmental data of the German rivers Saale, Ilm and Unstrut. Main aspects of the study are to describe the relationships of the distribution of metals between river water and river sediment using PLS. A simulation of the distribution of metals between the liquid and solid phase by variation of some parameters (e.g. conductivity, DOC, dissolved oxygen, pH, phosphate and suspended matter) is presented and compared with experimental results.     

Behaviour of long-lived Chernobyl radionuclides in a soil-water system.

Field and laboratory experiments have been used to study the behaviour of long-lived radionuclides in the zone affected by the Chernobyl accident. Speciation of 90Sr and 137Cs in soils and bottom sediments was determined. The principal distinction of the Chernobyl fallout was that it contained a relatively small proportion of exchangeable forms because a considerable fraction of the radionuclides was incorporated as part of the insoluble fuel particles. Disintegration of fuel particles in soils and bottom sediments results in transition of non-exchangeable forms into exchangeable forms. Radionuclide species have different pathways and rates of migration in soils and bottom sediments. Migration of each chemical form was described by a convective-dispersive equation taking into account transformation processes of radionuclide species in soils or bottom sediments. Adsorption of 90Sr and 137Cs in the environment is controlled by the cation-exchange capacity and the selectivity of the solid phase (i.e., soil, bottom sediments and suspended matter) and the cationic composition of the liquid phase (i.e., soil solution, surface run-off and river or lake water). The corresponding parameters for the processes were obtained.     

Investigation of radiocesium biokinetics in Manila clam (Ruditapes philippinarum)

This study was carried out to better understand the biokinetics of radiocesium in clams living in sediment. The accumulation and depuration kinetics of ¹³⁴Cs were investigated in the Manila clam (Ruditapes philippinarum) under controlled laboratory conditions. The concentration factor was found to be 3.0 for ¹³⁴Cs in the whole body; however, the concentration factor in the soft part of the clams (12) was significantly higher than those in the whole body and shell (0.80). The depuration kinetics of the radionuclide were described by a two-component exponential model for the whole body. The biological half-lives in the fast and slow components were found to be 0.63 and 22.1 days, respectively. The depuration kinetics for ¹³⁴Cs in the soft parts were described by a single-component exponential model with a resultant the biological half-life of 18.0 days.     

Assessing the deposition and remobilisation behaviour of metals between river water and river sediment using partial least squares regression

Partial least squares regression (PLS) as a method for multivariate data analysis has been applied to environmental data of the German rivers Saale, Ilm and Unstrut. Main aspects of the study are to describe the relationships of the distribution of metals between river water and river sediment using PLS. A simulation of the distribution of metals between the liquid and solid phase by variation of some parameters (e.g. conductivity, DOC, dissolved oxygen, pH, phosphate and suspended matter) is presented and compared with experimental results. Received: 15 July 1997 / Revised: 6 November 1997 / Accepted: 7 November 1997     

Analysis of water-soluble fraction of metals in atmospheric aerosols using aerosol counterflow two-jets unit and chemiluminescent detection

A new analytical system for a semi-continuous analysis of water-soluble fraction of particulate metals is described. The system combines the continuous sampling of atmospheric aerosols into deionized water using the Aerosol Counterflow Two-Jets Unit and on-line chemiluminescent detection of water soluble fraction of metals in collected aerosols. The potential of analytical system was studied using Fe³⁺, Cu²⁺ and Co²⁺ as model metals in atmospheric aerosols. The detection limits of particulate Fe³⁺, Cu²⁺ and Co²⁺ (S/N?=?3) are 24, 41 and 0.4?ng?m^?3, respectively. The presented set-up allows the determination of concentration of water-soluble fraction of particulate metals in ‘real time’ with time resolution of 30?min. The system is sufficiently robust for the field application. The method has been applied to the measurement of selected metals in urban TSP (Total Suspended Particles) aerosols in Brno in the Czech Republic. The concentrations of particulate water-soluble Fe³⁺, Cu²⁺ and Co²⁺ were found in the range of 35 to 290, 42 to 462 and 0.5 to 9?ng?m^?3, respectively.     

A laboratory approach for investigations into the potential effectiveness of potassium-based fertilisers in reducing radiocesium transfer from soil to plant

The paper presents a laboratory experimental model based on a simplesoil-plant system used to investigate the potential effectiveness of potassium-basedfertilisers in reducing soil-to-plant transfer of radiocesium. The soil-plantsystem, slightly modified comparing to that described originally in the NEUBAUER'splantlet method, consists in wheat plantlets grown from caryopsis phase onbrown acid soil contaminated with ¹³⁷Cs resulted from Chernobylnuclear accident and treated with potassium salt of 30%. The effectivenessof 30% potassium salt applied to the soil as treatment is discussed in termsof reduction factor for ¹³⁷Cs soil-to-plant transfer coefficientand ¹³⁷Cs ⁺ :K ⁺ ratio in soil and plantlets.     

Determination of soluble and insoluble nickel compounds in airborne particulate matter by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry

An extraction procedure for the determination of soluble and insoluble nickel and its compounds in ambient air dust was investigated employing a special device for the generation of test aerosols and using water-soluble NiCl2, partly water-soluble NiCO3 and water-insoluble NiO as model compounds. Additionally, results of the separation and determination of different nickel species down to some ng/m3 in ambient aerosols are discussed. The extraction was carried out with a solution containing 0.01 mol/L EDTA in order to determine partly water-soluble compounds such as NiCO3 and water-soluble, non-toxic nickel compounds in one step. Airborne dust was sampled on filters at locations close to two metallurgical plants in Northrhine-Westphalia (Germany), and first results on the nickel concentration (mean (median) values over a period of 4 months: 8.6+/-6.5 ng/m3 (6.7 ng/m3) and 27.7+/-36 ng/m3 (10.8 ng/m3), respectively) in the collected dust are presented. For EDTA-soluble nickel compounds the maximum and mean fractions of total nickel were found to be 77.1% and 18.6+/-12%, respectively.